This invention relates to file system storage. Documents can be stored in a hierarchical or tree-structured file system. A tree structure is a method for placing and locating files (called records or keys) in a database. The method typically finds data by repeatedly making choices at decision points called nodes. A node can have as few as two branches (also called children), or as many as several dozen.
In a tree, records are stored in locations called leaves. This name derives from the fact that records always exist at end points; there is nothing beyond them. The starting point is called the root. The maximum number of children per node is called the order of the tree. The maximum number of access operations required to reach the desired record is called the depth. When a hierarchical file system is used to store millions of documents, the tree structure will become very complex and difficult to navigate.